None of the EFT tapping points are required, per se. Each of the points that are a part of the short form of EFT was chosen for their ease of access, their connection to one or more meridians, and their proven effectiveness. The EFT manual also shows additional steps, like the 9 Gamut, that can be useful but that add time to the process without making it significantly more effective.
The top of the head was added by Gary and others to the short form because it is highly effective. The top of the head is a meeting place for several meridians. It is also a spiritual energy center (think “halo”). Gary used it each round during recent seminars I attended, starting there and ending under the arm.
I like the way the top of the head points feels. I start with it, and often end a round there as well. Carol Look starts rounds at the eyebrow and ends at the top of the head. Indeed, most EFT advanced practitioners include the top of the head now, in some way. If you find it physically uncomfortable to do it, just leave it out.